Loud Thunk Followed By Vibration!! Help!

Hey all - here's what I've got. 2004 22' Tracker Pontoon with an 3.0L Mercruiser and Alpha1 drive.

Yesterday we were out on the river for a few hours and just as we were getting back to the dock I heard a loud thunk come from the stern drive. It sounded like I hit a rock but I was still out in the middle of the channel.

Instantly there was a vibration in the steering wheel. It still ran however and we putted back to the dock. I recovered the boat out of the water and expected to see some dings in the prop. There was nothing though, either on the skeg or on the prop that indicated any contact with anything in the water.

When I turned the prop with my hand though there's a loud tick coming from just behind the prop. Also the trail of water that the boat brought up with it from the landing to where I strap it down had a nice rainbow, oily slick with it.

Help - where to start? What the heck did I do here?? Lower unit toasted?

Edit - according to the tank of gear lube in the engine bay, it is full and a nice green color.

Re: Loud Thunk Followed By Vibration!! Help!

Remove the drain screw on the drive and see what is on the magnet.

Re: Loud Thunk Followed By Vibration!! Help!

Don S said:

Remove the drain screw on the drive and see what is on the magnet.

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Damn damn damn damn... took out the plug and the green fluid is milky and there was a lot of shavings on the magnet.

So what does a new/rebuilt lower end unit cost? Btw this is the third time out since we bought the boat from a dealership - does anyone think they may be partly responsible for this?

Re: Loud Thunk Followed By Vibration!! Help!

In most cases when a drive explodes it was caused by a previous underwater strike up to 3 years ago.Chip a tooth, crack a tooth and when it locks the gears the torque has nowhere to go.Running low on oil tends to melt the gears rather than cleanly break them.A large plastic lawn bag can cause you to chip a gear let alone a log, rock or hard bottom. The one answer I hear most often is "But I didn`t hit anything this year".when questioned, he replaced 3 props last year.

Re: Loud Thunk Followed By Vibration!! Help!

beermunk said:

Btw this is the third time out since we bought the boat from a dealership - does anyone think they may be partly responsible for this?

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Only if a warranty was a part of your purchase agreement.

Re: Loud Thunk Followed By Vibration!! Help!

Not good. The sad thing is, those shavings are now throughout the upper as well, they share lubricant. You can pull the cap on top of the upper and inspect the top gears and see if that was where it failed. SE has a good price on outdrives. Lower about 700, both upper and lower around 1300. Just remeber, if the upper looks ok, the shavings have travelled and unless it's taken apart and cleaned, reinstalled, you will have shavings in your new lower. Also, Unless the dealer sold you a warranty, they probably won't be much help as far as cost of repair.

Re: Loud Thunk Followed By Vibration!! Help!

searay3 said:

Not good. The sad thing is, those shavings are now throughout the upper as well, they share lubricant. You can pull the cap on top of the upper and inspect the top gears and see if that was where it failed. SE has a good price on outdrives. Lower about 700, both upper and lower around 1300. Just remeber, if the upper looks ok, the shavings have travelled and unless it's taken apart and cleaned, reinstalled, you will have shavings in your new lower. Also, Unless the dealer sold you a warranty, they probably won't be much help as far as cost of repair.

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What is SE?

Re: Loud Thunk Followed By Vibration!! Help!

SE= Sterndrive Engineering, aftermarket outdrives.

If you heard a loud thud/thunk followed by the vibration did you think you might have hit something? I know you didn't see damage when you looked. Maybe you should call your insurance agent and explain what happened. Possibly your untrained eye did not see evidence of an impact. I'm assuming a just bought 2004 has insurance.

James

Re: Loud Thunk Followed By Vibration!! Help!

took out the plug and the green fluid is milky and there was a lot of shavings on the magnet.

Click to expand...

Pull the outdrive and check the bellows for water.

Re: Loud Thunk Followed By Vibration!! Help!

Well I've got some very good news from the insurance adjuster and the mechanic.

They looked at both the upper and lower unit and found that both are in perfect condition. Apparently there is a bad seal that blew out ($120 to fix) and that is why water was in the gear lube. The mechanic said it was probably bad before we bought the boat.

The loud THUNK and subsequent vibration was caused by hitting an underwater piece of wood. It didn't do any damage to the paint on the skeg or prop but the prop blades are bent (I did notice this) thus causing the vibration.

The adjuster checked the "prop out?" on the shaft and said it's still within 1000 of the manufacture specs. He also said the filings I saw were normal sized.

Sooo... no $500 deductible to pay! $120 of parts and labor to replace the seals and she'll be ready by the weekend. Yea!

Re: Loud Thunk Followed By Vibration!! Help!

Glad to hear it worked out OK.